Packaging machine and method of forming packages

ABSTRACT

A machine and method for evacuating sealed packages formed from flexible sheet material which may be heat sealed, and for sealing the package. A heat-sealing device has two sections disposed opposite each other and movable toward each other to seal two sheets of the flexible material together to form a sealed package. One of the sections comprises a suction head for applying vacuum to one of the sheets of flexible material to cause the one sheet to move toward a knife member fixedly secured in the suction head to form a pierced opening in the one sheet through which air is exhausted from the package through the pierced opening. A heat-sealing member is disposed in and reciprocable in the suction head for movement between a retracted position and an extended sealing position. The heat-sealing member is adapted to heat seal the sheets together in an area surrounding the pierced opening when in its extended position. In the preferred form of the invention, the other section of the heat-sealing device also comprises a vacuum head for applying suction to the other sheet of flexible material to grip the other sheet while the one sheet is being pierced and the air is evacuated from the package.

United States Patent Young et al.

[ 1 Dec. 19, 1972 [54] PACKAGING MACHINE AND METHOD OF FORMING PACKAGES [72] Inventors: William E. Young, Stamford, Conn.;

Arthur D. Jezuit, Wood Dale, Ill.

[73] Assignees: W. R. Grace & Co., Duncan, S.C.;

John Morrell 8: Co., Chicago, Ill.

[22] Filed: March 3, 1971 [21] Appl. No.: 120,512

[52] US. Cl. ..53/112 R, 53/112 A [5 l] Int. Cl. ..B65b 31/02 [58] Field of Search ..53/22 R, 22 A, 22 B, 112 R,

[56] References Cited UNITED STATES PATENTS 3,026,656 3/1962 Rumsey ..'...53/22 3,347,011 10/1967 Lovas et a]. ..53/22 A Primary Examiner-Travis McGehee Attorney-Hofgren, Wegner, Allen, Stellman & Mc- Cord [57] ABSTRACT A machine and method for evacuating sealed packages formed from flexible sheet material which may be heat sealed, and for sealing the package. A heat-sealing device has two sections disposed opposite each other and movable toward each other to seal two sheets of the flexible material together to form a sealed package. One of the sections comprises a suction head for applying vacuum to one of the sheets of flexible material to cause the one sheet to move toward a knife member fixedly secured in the suction head to form a pierced opening in the one sheet through which air is exhausted from the package through the pierced opening. A heat-sealing member is disposed in and reciprocable in the suction head for movement between a retracted position and an extended sealing position. The heat-sealing member is adapted to heat seal the sheets together in an area surrounding the pierced opening when in its extended position. In the preferred form of the invention, the other section of the heat-sealing device also comprises a vacuum head for applying suction to the other sheet of flexible material to grip the other sheet while the one sheet is being pierced and the air is evacuated from the package.

7 Claims, 11 Drawing Figures PATENTED DEC 19 I972 SHEET 2 BF 6 TxQN QmRQOUM PATENTED DEC 19 m2 sum 3 BF 6 PACKAGING MACHINE AND METHOD OF FORMING PACKAGES BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to a machine and method for evacuating sealed packages having a flexible wrapper of which at least the inner surface is heat sealable and for sealing the package.

Food products and other commodities are marketed in flexible sheet material or film made of air and moisture impervious plastic, the packages being formed either from precut sections of the flexible material or from a continuous length thereof. Some of the products so marketed are adversely affected by their exposure to air for a length of time, but they retain their desired characteristics if maintained in a package from which the air has been evacuated.

Various machines or procedures have been utilized to evacuate packages of the character described after inserting into the packages the food products or other commodities. In one type of machine, the packages containing the products are fed to a vacuum chamber, the chamber is sealed, and the air is evacuated from the chamber. Upon arriving at the desired vacuum, the package which has been subjected to the vacuum within the chamber is sealed off by heat-sealing means. With such machines, a slit must be formed in the package before the package is fed to the vacuum chamber, thus creating adjustment problems for the slitter with different sizes and shapes of packages.

In other types of machines the package is completely closed or sealed after the products have been inserted therein, a hole is punched through the package, and the air within the package is evacuated through the punched hole. The area of the package surrounding the hole then is sealed off, and the package thus is maintained hermetically sealed.

Examples of machines of the last-mentioned type may be seen by reference to the U.S. Pats. to Gebhardt Nos. 2,888,788 and 2,896,385. With the machine disclosed in these two patents, a hole is punched through one sheet of the film which forms the package by means of a knife disposed in a suction line, so that the punching of the hole is brought about by a suction effect applied to the one sheet of film. Not only are the two sections of the heating device in said structures relatively movable to seal the package, but the knife is mounted for axial movement in one of the sections which forms a suction head at the end of a suction line. The knife must be withdrawn into the suction head after piercing the one sheet of film, resulting in a complicated machine, as well as one which is difficult to control in respect to coordinating the sequence of suction application and movement of the knife blade. It is a solution for such problems that the present invention is directed.

It is, therefore, one object of the present invention to provide a new and improved apparatus of the character described for evacuating a sealed package and for sealing the package.

Another object of the invention is to provide an apparatus for evacuating a sealed package formed of two opposite sheets of flexible material capable of being heat sealed and for sealing the package, including a frame and a heat-sealing device carried by the frame.

The heat-sealing device has two sections disposed opposite each other and movable toward each other to seal the two sheets, one of the sections constituting a suction head. A knife means is disposed in and immovable relative to the suction head, and is adapted to pierce one of the sheets upon subjecting the one sheet to a suction effect from the suction head. A vacuum means is connected with the suction head to apply suction thereto to cause the one sheet to move toward the knife means to form a pierced opening in the one sheet and to exhaust air from between the sealed sheets. A heat-sealing member is disposed in and reciprocable in the suction head for movement between a retracted position and an extended sealing position, the heatsealing member being adapted to heat seal the two sheets together in an area surrounding the pierced opening after the air is evacuated. The heat-sealing member surrounds the knife means and is resiliently urged toward its-retracted position.

In the preferred embodiment of the invention, the other section of the heat-sealing device, referred to above, also comprises a suction head, and vacuum means is connected with the othersection to apply suction thereto to grip the other sheet of flexible material while the one sheet is being pierced and the air is being evacuated from between the sheets. Control means is provided to apply the vacuum to the other section of the heat-sealing device prior to applying the vacuum to the first section, the vacuum to both sections being released simultaneously after the sheets are heat sealed in the area surrounding the pierced opening.

A further object of the invention is to provide a method of evacuating a sealed package, as described herein.

Other objects, features and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a packaging machine embodying the concepts of the present invention;

FIG. 2 is a schematic elevational view illustrating the machine part or station arrangement of the packaging machine shown in FIG. 1;

FIG. 3 is a partial plan view of the machine, on an enlarged scale, taken generally along the line 33 of FIG. 1;

FIG. 4 is a vertical section taken generally along the line 4-4 of FIG. 3;

FIG. 5 is a vertical section taken generally along the line 5-5 of FIG. 4;

FIG. 6 is a vertical section, on an enlarged scale, taken generally along the line 6-6 of FIG. 4;

FIG. 7 is a vertical section taken generally along the line 7-7 of FIG. 6; and

FIGS. 8 through 11 are sequential schematic views of the sealing and evacuating head, as seen in detail in FIG. 6, to facilitate an understanding of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings in greater detail, and first to FIGS. 1 and 2, a packaging machine, generally designated 15 in FIG. 1, is shown and is designed to package food products or other commodities in packages formed from flexible sheet material or film which is capable of being heat sealed about the product. Referring to FIG. 2, one continuous film F is stripped off of a lower supply roll'l6 of heat-scalable flexible material and is carried successively to a forming station 18 where individual pockets P or clusters thereof are formed in the film for receiving a product to be packaged, then to a loading station 20 where the product is loaded or positioned in the pockets P, normally by hand, and then to a sealing and evacuation station 22. A second continuous sheet or layer of film F is carried from an upper film supply roll 24 of heatsealable flexible material 'to a point between the loading station 20 and the sealing and evacuating station 22, to overlie the lower film sheet F and the pockets P formed therein, with the product loaded in the pockets. The juxtaposed lengths of film then are carried to the sealing and evacuating station 22 where the sheets are heat sealed together about the periphery of the pockets P and air is evacuated from within the pockets to provide moisture and air-impervious packages. The sealed pockets then are carried to a cutter 26 where the webs of film between the individual pockets are cut. The waste film is carried from the cutting station by a vacuum nozzle 28, and the severed filled and sealed packages are carried therefrom as by a conveyor 30.

Should either the upper or lower sheets of film F and F, respectively, be printed along the length thereof for each package, film registration means or stations 33 for the upper sheet of film F and 33 for the lower sheet of film F' may be provided to index the film so that the printing thereon is properly aligned for each ultimately sealed and loaded package.

The present invention deals primarily with a new and improved apparatus at the sealing and evacuating station 22 for sealing the upper and lower sheets of film together about each individual loaded pocket P and for evacuating the air from within the sealed pocket to provide an air and moisture impervious package.

Referring to FIGS. 3 through 7, the apparatus at the sealing and evacuating station includes a heat-sealing device generally designated 32 mounted on the frame of the machine 15 and having upper and lower sections 32a and 32b, respectively. The two sections 32a, 32b of the heat-sealing device are disposed opposite each other, as best seen in FIGS. 6 and 7, and the lower section 32b is vertically reciprocable relative to the upper section 32a by means shown in FIGS. 4 and (described in greater detail hereinafter).

The lower section 32b of the heat-sealing device 32, in the embodiment of the invention illustrated in the drawings, has a pair of wells 34 separated by a partition 36 for receiving a pair of pockets P formed in the lower sheet of film F at the forming station 18. The pockets will have been loaded with the product at the loading 1 between the wells, the insert members 38, 40 being provided as backing members to facilitate heat sealing the two sheets or layers of film together when the lower section 32b is moved upwardly into engagement with the upper section 32a which comprises a heating section, as described in greater detail hereinafter.

The lower section 32b of the heat-sealing device 32 has interior passages 42 in the base thereof communicating with the wells 34 at the bottom thereof and in communication with a vacuum hose or conduit 44 connected with an appropriate vacuum source for applying suction to the lower sheet of film F to grip the film during air evacuation of the packages.

FIGS. 4 and 5 show the means for mounting the lower section 32b of the heat-sealing device 32 for vertical reciprocating movement into and out of engagement with the upper section 32a of the heat-sealing device 32. The lower section 32b is journalled on vertical guide shafts 46 which form part of mounting brackets 48 secured to side wall portions 50 of the frame of the packaging machine 15. A linkage structure, generally designated 52, is disposedbetween the lower section 32b of the heat-sealing device and a bottom wall portion 54 of the frame of the packaging machine 15. The linkage structure has four link members 52a through 52d which effect vertical movement of the lower section 32b in response to rotation of a cam member 57 (FIG. 4). The link 52a is elongated, is pivotally connected at one end thereof to the underside of the lower section' 32b, and is pivotally connected at the other end thereof to one end of elongated link 52b. The other end of link 52b is pivotally connectedto the bottom wall portion 54 of the machine frame. Link member 520 also is elongated, is pivotally connected at one end thereof intermediate the ends of the link 52b, and is pivotally connected at the other end thereof to link 52d which is tria'ngularly shaped. One corner of the triangularly-shaped link 52d is connected to the link 52c, another corner thereof is pivotally connected to the base wall portion 54, and the third corner thereof has a roller member 55 positioned in a slot 56 of a cam member 57. The cam slot 56 has a rise portion 56a and a fall portion 56b. Thus, as the cam member 57 is rotated in the direction of arrow A, for instance, the rise portion 56a of the cam slot 56 pivotally cams the link 52d in the direction of arrow B (FIG. 4). The link 524, through the link 520, will cause the link 52b to pivot about its connection to the base wall portion 54 in the direction of arrow C. The link 52b in turn causes the lower end of link 52a to move outwardly in the direction of arrow D to pull the lower section 32b of the heat-sealing device 32 downwardly in the direction of arrow E away from and out of engagement with the upper section 32a. When the roller member 55 on the triangularly-shaped link 52d moves back into the fall portion 56b of the cam slot 56, as seen in FIG. 4, the links 52a-52d will be urged in directions opposite that described above, causing the lower section 32b of the heat-sealing device 32 to move into engagement with the upper section 32a.

Referring particularly to FIGS. 6 and 7, the upper section 320 of the heat-sealing device 32 comprises a heating and suction head to effect a heat seal between the layers or sheets of film F, F" about the pockets P formed therein, and for evacuating the air from between the sealed sheets. More particularly, the upper section 32a of the heat-sealing device 32 is fabricated of heat-conductive material and has an electrical heating element 58 embedded therein so as to distribute the heat from the heating element 58 through the body of the upper section 32a. Theheating element 58 is connected through an electrical cable 59 (FIG. 6) through a conduit 59a to an appropriate electrical source. To facilitate a heat seal, the upper section 32a has a downwardly depending lip 60 (FIG. 6) about the periphery thereof and overlying the resilient insert members 38 in the lower section 32b. The upper section 32a also has downwardly depending lips which extend inwardly, as at 62 in FIG. 7, over the upper edge of the partition 36 of the lower section 32b generally approximately one-fourth of the length of the partition 36 at each end thereof. The downwardly protruding lips 62 overlie the resilient insert members 40 (FIG. .7) disposed in the partition 36 of the lower section 32b of the heat-sealing device. Thus, it can be seen that as the rotatable cam 57 moves the lower section 32b upwardly toward the upper section 32a, the juxtaposed sheets of film F and F" will be sandwiched between the sections of the heat-sealing device and will be heat sealed in the areas defined by the lips 60, 62 of the upper section 32a and the resilient insert members 38, 40 of the lower section 32b. Insulating plate members 65 are provided on the underside of the upper section 32a to insulate the remaining areas of the upper sheet of film from the heated body portion of the upper section.

A knife blade 66 is disposed in and immovable relative to the upper section 320 of the heat-sealing device and is adapted to pierce the upper sheet of film F" upon subjecting the upper sheet to a suction effect from the upper section 32a, as described hereinafter. The knife blade 66 is secured to a downwardly depending shaft 68 rigidly secured in an upper wall portion 70a of a sleeve 70 which is rigidly mounted on an upper mounting block 72 of the heat-sealing device. The sleeve 70 has a plurality of openings 70b in communication with interior passage means 74 (FIG. 7) within the mounting block 72. The passage means 74 in the mounting block leads to a vacuum hose or conduit 76 which is connected to an appropriate vacuum source. Appropriate seals 77 are provided about the sleeve 70 above and below the openings 70b and the passage means 74 to prevent seepage of air when suction is applied. Thus, it can be seen that as vacuum is applied to the hose 76, suction will be created in the sleeve 70 and thereby subject the top sheet of film F" within the upper section 32a to a suction effect. The suction will cause the top sheet to move toward the knife 66 to form a pierced opening in the top sheet F". Continued application of suction will cause the air to be evacuated from between the sealed sheets of film (i.e. from within the pockets P disposed within the wells 34 of the lower section 32b of the heat-sealing device) through the pierced opening in the top sheet of film. The evacuated air passes around the knife blade 66 and through the openings 70b into the passage means 74 in the mounting block 72.

Continuing to refer particularly to FIGS. 6 and 7, the piercing knife blade 66 is surrounded by a heat-sealing member 78 disposed in and reciprocable in the upper section 32a, the heat-sealing member 78 being adapted to heat seal the sheets of film in an area surrounding the opening pierced in the upper sheet of film after the air is evacuated from between the sheets. More particularly, the heat-sealing member 78 has an electrical heating element 80 embedded therein and the member 78 is fabricated of heat-transferable material so as to dissipate the heat from the heating element. The heating element 80 is connected through an electrical cable 82 through a conduit 84 to an appropriate electrical source. The heat-sealing member 78 is movable between a retracted position shown in FIG. 7 to an extended sealing position wherein the heat-sealing member moves downwardly in the direction of arrows G to sandwich the sheets of film F, F" between the heat-sealing member 78 and resilient insert members 79 (FIG. 6) which are embedded in the partition 36 of the lower section 32b, surrounding the piercing knife blade 66.

To effect vertical reciprocation of the heat-sealing member 78, a pair of shafts 86 extend upwardly from the member 78 and are journalled in sleeves 88 disposed in the mounting block 72. A connectingbar 90 is connected to and spans the upper ends of the shafts 86. As best seen in FIG. 6, a piston-cylinder device having a piston 92 and a cylinder 94 is mounted on top of the mounting block 72. Passage means 96 (FIG. 6) is formed within the mounting block 72. The passage 96 is in communication with the interior of the cylinder 94 at the bottom thereof and'leads to an air hose or conduit 98 which leads to an appropriate source of air pressure. A piston rod 100 extends upwardly from the piston 92 through the upper wall of the cylinder 94. A lever member 102 is pivotally mounted on a shaft 104, as best seen in FIG. 6, and rests at one end on top of the piston rod 100 and at its opposite end on top of the connecting bar 90. Thus, as air pressure is admitted to the cylinder 94 on the underside of the piston 92, the piston will move upwardly in the direction of arrow H (FIG. 6) and, through the piston rod 100, cause the lever member 102 to pivot about shaft 104 in the direction of arrow I to exert a downward force on the connecting bar 90, and thus a downward force on the shafts 86 and heat-sealing member 78. The heat-sealing member thereby is moved downwardly into its extendedsealing position. As the heat-sealing member moves from about the knife toward its extended sealing position, the sealing member strips the film from about the knife and moves the film back to its original plane (i.e. prior to applying suction to the film) where it is heat sealed to the lower film F over the partition 36. With this structural arrangement, the two sheets of film are heat sealed in their original plane and there is no resulting distortion of the formed package. Coil springs 106 are disposed about the shafts 86 to urge the heat-sealing member 78 back to its retracted position when the air pressure is released from the cylinder 94 on the underside of the piston 92.

After the'two continuous sheets or layers of film from the upper and lower supply rolls thereof have passed through the forming and loading stations and have reached the sealing and evacuating station, with pockets P formed in the lower sheet of film F loaded with the product, and with the upper sheet of film disposed in juxtaposition above the lower sheet. The sealing and evacuating process of the present invention is as follows. The lower section 32b of the heat-sealing device 32 is raised by means of the linkage structure 52 and the cam 57 (FIGS. 4 and 5) into sealing position beneath the upper section 32a, as best seen in FIGS. 6 and 7, with the sheets of film sandwiched between the downwardly depending lips 60 and 62 of the upper section 32a and the insert members 38 and 40, respectively, of the lower section 32b. The sheets of film, with the pocket P in the lower sheet thereof within the wells 34 of the lower section 32b, thus are sealed about the periphery thereof and partially-along the partition 36 between the wells of the lower section 32b. Suction then is applied to the lower sheet of film F through the vacuum hose 44 and passages 42 at the underside of the lower section 32b of the heat-sealing device to grip the lower sheet of film. Suction then is applied through the vacuum hose 76, passage means 74 in the mounting block 72, and openings 70b in the sleeve 70 to the upper sheet of film to causethe upper sheet to move upwardly toward the knife blade 66 to form a pierced opening in the upper sheet. The suction on the upper sheet is continued to exhaust the air from between the two sealed sheets. Air pressure then is admitted to the bottom of the cylinder 94 beneath the piston 92 to cause the heat-sealing member 78 to move downwardly in the direction of arrows G (FIGS. 6 and 7), stripping the film from about the knife blade 66 and heat sealing the two sheets of film in an area surrounding the pierced opening formed by the knife blade, with the two sheets of film generally in their original planes (i.e. prior to applying the suction thereto). The vacuum applied to both the upper and lower sections 32a and 32b, respectively, of the heat-sealing device 32 is released simultaneously so that the two sheets of film will retract and cling snuglyagainst the products contained in the pockets formed between the two sheets of film. The air pressure in the cylinder 94 then is released so that the heat-sealing member 78 is biased back to its retracted position by the springs 106. The lower section then is retracted and the sealed and evacuated packages are separated by the cutter 26 and conveyed fromthe machine.

FIGS. -8 through 11 show schematically the above sequence of steps of evacuating the air from between the two sheets of film. FIG. 8 shows suction being applied to the lower section of the heat-sealing device to grip the lower sheet of film; suction being applied to the upper section of the heat-sealing device to draw the upper sheet of film into piercing engagement with the knife blade, and with the heat-sealing member surrounding the knife blade disposed in its retracted position. FIG. 9 is similar to FIG. 8 and shows the upper sheet of film having been pierced and the air from between the-sheets of film being evacuated through the pierced opening. FIG. 10 shows the heat-sealing member which surrounds the knife blade moved downwardly relative to the knife blade to strip the upper sheet of film from the knife and heat seal the two sheets of film in an area surrounding the pierced opening with the upper sheet returned to the plane of the top of the packages. FIG. 11 is a view similar to- FIG. 10, with the vacuum released on the two sheets of film so that the film retracts and clings to the product packaged therebetween.

A control box 110 (FIGS. 1 and 3) is disposed behind the sealing and evacuating station 22 and houses control means including an appropriate conventional electrical cam, appropriate conventional, solenoidoperated air and vacuum valves, and appropriate pneumatic and electric circuitry to control the timing of the vacuum for the lower section 32b of the heat-sealing device, the vacuum for the upper section 32a, and the air pressure applied to the cylinder 94. The cam is synchronized with the cam 57. It should be noted that the packaging machine described above is adapted to form clusters of two pockets P side by side in the lower continuous sheet of film F, as best seen in FIG. 3. However, it should be understood that the machine, and particularly the means and method of sealing and evacuating the packages, is equally adaptable for a wide variety of package shapes and clusters.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom as some modifications will be obvious to those skilled in the art.

We claim:

1. An apparatus for evacuating asealed package formed of two opposite sheets of flexible material capable of being heat sealed and for sealing said package, comprising: a frame, a heat-sealing device carried by said frame and having two sections disposed opposite each other and movable toward each other, one of said sections constituting a suction head, the other of said sections having a pair of wells for holding one sheet of said flexible material with a load of product in each well and a partition extending between said wells against which a portion of the last-mentioned sheet engages, a knife means disposed in and immovable relative to said suction head and overlying said partition at a distance therefrom and adapted to pierce the other of said sheets upon subjecting said other sheet to movement toward the knife means by a suction effect from said suction head, vacuum means connected with said suction head to apply suction thereto 'to cause the other sheet to move toward said knife means to form a pierced opening in said other sheet and to exhaust air from between said sheets, vacuum means connected to the other of said sections to hold said one sheet against the partition and prevent movement and piercing thereof, and a heat-sealing member disposed in and reciprocable in said suction head and overlying said partition for movement between a retracted position and an extended sealing position pressing both said sheets against said partition, said heat-sealing member being adapted to heat seal said sheets in an area surrounding said pierced opening when in said sealing position.

2. The apparatus of claim 1 including resilient means for urging said sealing member toward its retracted position.

3. The apparatus of claim 1 wherein said one section is fixed to said frame and the other of said sections is movably mounted on the frame for movement into sealing position with said one section.

4. The apparatus of claim 1 wherein said heat-sealing member surrounds said knife means and strips the other sheet from. about the knife while moving toward its extended sealing position. I

5. The apparatus of claim 4 wherein said vacuum means applies suction between said knife means and said sealing member.

6. The apparatus of claim 1 including control means to apply vacuum to said other section prior to applying vacuum to said one section.

7. An apparatus for sealing and evacuating a package formed from two opposite sheets of heat sealable flexible material comprising, a pair of relatively movable parts having means at their perimeter for engaging and sealing the sheets together to form a perimeter seal for the package, one of said parts constituting a sealing head and the other part constituting a package-holding head, said package-holding head having a support member against which a portion of one sheet of said material engages, vacuum means connected to said package-holding head for holding said package against movement and said sheet portion against the support member during evacuation of the package, said suction head having a slitting knife overlying and spaced from said support member, vacuum means connected to said suction head to draw a part of the other sheet of material away from said one sheet and form an evacuation opening therein and then evacuate the package through said opening, and heat sealing means movable past the knife and toward the support member to return said other sheet into engagement with said one sheet and heat seal the sheets together by pressure against said support member. 

1. An apparatus for evacuating a sealed package formed of two opposite sheets of flexible material capable of being heat sealed and for sealing said package, comprising: a frame, a heat-sealing device carried by said frame and having two sections disposed opposite each other and movable toward each other, one of said sections constituting a suction head, the other of said sections having a pair of wells for holding one sheet of said flexible material with a load of product in each well and a partition extending between said wells against which a portion of the lastmentioned sheet engages, a knife means disposed in and immovable relative to said suction head and overlying said partition at a distance therefrom and adapted to pierce the other of said sheets upon subjecting said other sheet to movement toward the knife means by a suction effect from said suction head, vacuum means connected with said suction head to apply suction thereto to cause the other sheet to move toward said knife means to form a pierced opening in said other sheet and to exhaust air from between said sheets, vacuum means connected to the other of said sections to hold said one sheet against the partition and prevent movement and piercing thereof, and a heat-sealing mEmber disposed in and reciprocable in said suction head and overlying said partition for movement between a retracted position and an extended sealing position pressing both said sheets against said partition, said heat-sealing member being adapted to heat seal said sheets in an area surrounding said pierced opening when in said sealing position.
 2. The apparatus of claim 1 including resilient means for urging said sealing member toward its retracted position.
 3. The apparatus of claim 1 wherein said one section is fixed to said frame and the other of said sections is movably mounted on the frame for movement into sealing position with said one section.
 4. The apparatus of claim 1 wherein said heat-sealing member surrounds said knife means and strips the other sheet from about the knife while moving toward its extended sealing position.
 5. The apparatus of claim 4 wherein said vacuum means applies suction between said knife means and said sealing member.
 6. The apparatus of claim 1 including control means to apply vacuum to said other section prior to applying vacuum to said one section.
 7. An apparatus for sealing and evacuating a package formed from two opposite sheets of heat sealable flexible material comprising, a pair of relatively movable parts having means at their perimeter for engaging and sealing the sheets together to form a perimeter seal for the package, one of said parts constituting a sealing head and the other part constituting a package-holding head, said package-holding head having a support member against which a portion of one sheet of said material engages, vacuum means connected to said package-holding head for holding said package against movement and said sheet portion against the support member during evacuation of the package, said suction head having a slitting knife overlying and spaced from said support member, vacuum means connected to said suction head to draw a part of the other sheet of material away from said one sheet and form an evacuation opening therein and then evacuate the package through said opening, and heat sealing means movable past the knife and toward the support member to return said other sheet into engagement with said one sheet and heat seal the sheets together by pressure against said support member. 